Thermal circuit breaker



A ril 1, 1969 P. R. HEANEY 3,436,712

' THERMAL CIRCUIT BREAKER Filed June 27, 1967 FIG.2

PAUL R. HEANEY INVENTOR.

BY 42M ATTORNEYS United States Patent U.S. Cl. 337-405 4 Claims ABSTRACT OF THE DISCLOSURE A thermal circuit breaker for opening an electrical circuit when the ambient temperature surrounding the circuit breaker exceeds a predetermined temperature.

Background of the invention This invention relates generally to thermal circuit breakers, and more specifically to an improved thermal circuit breaker of the type in which a pair of electrical conductive members biased toward one another grip therebetween a bar of metal having a low melting point. When the ambient temperature surrounding the circuit breaker exceeds the melting point of the metal, the bar fuses or melts and the electrical circuit between the members is broken.

Thermal circuit breakers of the type having a replaceable fusible plug interconnecting a pair of electrically conducting spring arms for breaking the electrical circuit when the plug fuses are generally well known in the art. Circuit breakers of this general type are disclosed in US. Patents 1,910,945 and 2,149,773. However, both of the circuit breakers disclosed in the aforementioned patents have the disadvantage of requiring a fusible plug of a predetermined shape and configuration. In US. Patent 1,910,945, the fusible plug must be C-shaped in order for the circuit breaker to be operative. In US. 2,149,773, the fusible plug must be I-shaped in order to accomplish its intended function and to be operative. Applicants in vention, on the other hand, is operative with any type of elongated, bar-shaped fusible plug.

Summary of the invention This invention icludes within its scope a thermal circuit breaker having a conductive, fusible plug gripped by a pair of members resiliently biased toward one another. When the ambient temperature surrounding the circuit breaker exceeds the melting point of the metal plug, the plug fuses and the electrical circuit is broken. The circuit is restored by inserting a new fusible plug between the members.

One of the objects of the present invention is to provide an improved thermal circuit breaker having a pair of members biased toward one another for gripping an elongated, bar-type fusible plug interposed therebetween.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a top plan view of a preferred embodiment of the improved thermal circuit breaker of this invention; and

FIG. 2 is a section view taken along line 22 of FIG. 1.

Description of the preferred embodiment Referring to the drawing, a thermal circuit breaker 4 of this invention comprises a base member 6 of insulating material having a pair of posts 8, 10 extending from one See surface thereof as best seen in FIG. 2. An electrically conductive plate 12 having a pair of elongated openings 14 for receiving posts 8, 10 is mounted on base 6. The plate 12 has a pair of resilient fingers 16 extending therefrom provided with curved ends 18 biased in a direction for gripping one side of a fusible, electrically conductive plug 20. The fusible plug 20 may be formed from any bar of metal alloy, and the temperature at which the plug fuses is determined by the selection of the alloy.

A wafer 22 constructed of any suitable insulating material and having openings therein for receiving posts 8, 10 is mounted on plate 12. An electrically conductive plate 24 similar to plate 12 and having a pair of elongated slots 26 for receiving posts 8, 10 is mounted on insulating wafer 22, which separates plates 12, 24 preventing any short circuit therebetween. The component parts of circuit breaker 4 are secured together by insulating washer 28 and screw 30 engaging a threaded bore in post 10. The plate 24 has a pair of resilient fingers 32 extending therefrom having curved ends 34 biased toward plate 12 for engaging the opposite side of fusible plug 20.

The elongated slots 14, 26 in plates 12, 24 permit adjustable movement of the plates relative to one another to place the curved ends 18, 34 of fingers 16, 32 respectively in register. Although plates 12, 24 are shown as provided with elongated slots 14, 26 respectively, such slots need to be provided in only one plate. However, from the standpoint of increased efiiciency in manufacture and construction, plates 12, 26 are preferably identically constructed such as by a stamping operation from common stock material, and then one of the plates reversed in the assembling operation. In the assembled position, fingers 16, 32 are laterally spaced apart so that in the event plug 20 fuses, the resilient fingers 16, 32 will not engage one another as they move to their unflexed position. The opposite end of each of the plates 12, 24 is provided with lugs 36, 38 respectively to which electrical wires of any electrical circuit are connected in the normal manner.

The invention has been described in detail with particular reference to one embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. In a thermal circuit breaker, the combination comprising:

a support member of electrically insulating material,

a first plate of electrically conducting material mounted on said support member,

said first plate having a first finger projecting therefrom for engaging one surface portion of an elongated fusible plug capable of fusing at a predetermined temperature,

a Second plate of electrically conducting material mounted on said support member and insulated from said first plate,

said second plate having a second finger for engaging the opposite surface portion of the fusible plug, said second finger projecting from said second plate substantially parallel to said first finger and laterally spaced therefrom in a direction transverse to the direction of projection of said fingers,

means for biasing one of said first and second fingers toward the other finger for gripping the fusible plug therebetween, and

means for mounting one of said first and second plates for movement with respect to the other of said plates to provide for relative adjustment of said plates and for positioning the plug engaging portions of said first and second fingers in substantial alignment.

2. The invention according to claim 1 wherein said biasing means comprises forming one of said first and second fingers of a resilient material biased toward said other finger.

3. In a thermal circuit breaker, the combination comprising:

a support member of electrically insulating material having a base from which a pair of ports project;

a first plate of electrically conducting material mountable on said base and having openings therein through which said posts extend;

said first plate having a first finger projecting therefrom for engaging one surface portion of an elongated fusible plug capable of fusing at a predetermined temperature;

an electrically insulating member mountable on said first plate and having openings therein through which said posts extend;

a second plate of electrically conducting material mountable on said insulating member and having openings therein through which said posts extend;

said second plate having a second finger projecting therefrom for engaging the opposite surface portion of the fusible plug, said second finger projecting from said second plate substantially parallel to said first finger and laterally spaced therefrom in a direction transverse to the direction of projection of said fingers;

means for securing said first plate, insulating member and second plate to said support member;

means for biasing one of said first and second members toward the other finger for gripping the fusible plug therebetween; and

said openings in one of said first and second plates being elongated to provide for relative adjustment of said plates and for positioning the plug engaging portions of said first and second fingers in substantial alignment.

4. The invention according to claim 3 wherein said biasing means comprises forming one of said first and second fingers of a resilient material biased toward said other finger.

References Cited UNITED STATES PATENTS 2,004,773 6/1935 Sonn 200-142 2,531,115 11/1950 Doak 200117 2,873,347 2/1959 Boggs 200-123 X 2,917,606 12/1959 Durland 200-142 BERNARD A. GILHEANY, Primary Examiner.

HIRAN B. GILSON, Assistant Examiner.

US. Cl. X.R. 3 37401 

